1. Field of the Invention
The present invention relates to an image forming paper for forming a color image, particularly, a full-color image thereon by an image forming apparatus using a plurality of color toners, such as an electrophotographic apparatus and an ink-jet printer, and an image forming process using the image forming paper.
2. Description of the Related Art
Conventional image forming paper has been manufactured in pursuit of visual whiteness as mentioned in "Measurement of Paper Whiteness", Printing Magazine, Vol. 71, No.7 (1988), pp. 31-40. Since a paper is visually regarded as whiter as its reflectance for a blue component of light having a wavelength range of from 430 nm to 570 nm is higher, developments have been made to increase the reflectance for the blue component.
Since a reflectance of paper for light having a wavelength of 457 nm is defined as a value of whiteness, it is considered that the increase of the reflectance for the blue component leads to higher whiteness.
The whiteness as the reflectance for light having a wavelength of 457 nm is increased by bleaching paper to remove color development by impure colored substances, adding a large amount of blue dye to increase the reflectance for blue, and adding a small amount of blue fluorescent dye to further increase the reflectance for blue.
However, since a large amount of blue dye is added in the above-mentioned related art, the reflectance is decreased in regions from green to red (wavelength range of from 500 nm to 700 nm) as shown in FIG. 4. Although the addition of blue dye increases the whiteness of paper, it lowers color reproducibility of a color toner image formed on the paper in green to red regions, and, in particular, lowers color chroma. Color appears because a component having a specific wavelength of light radiated from an outside source is absorbed in passing through color toner laid on paper and components of the light having other wavelengths are reflected by the paper, passed again through the color toner and diffused outside the paper. Therefore, low reflectance of paper for the green to red regions means that the amount of light diffused out of toner, which transmits the wavelength components of such color (green to red), decreases, that is, the color is subdued. In other words, the chroma of color having wavelength components from green to red decreases.